JP6056718B2 - Metal strip rolling method - Google Patents

Description

  The present invention is a metal strip rolling line such as a hot rolling line or a cold rolling line, and has a shape in which the roll profile has a curve represented by a function of the third order or higher, and complements each other vertically in the axial position. The present invention relates to a rolling method of a metal strip that is rolled by shifting a pair of upper and lower work rolls in axial directions opposite to each other by a rolling mill having a pair of upper and lower work rolls formed by the initial roll curve.

  In rolling a metal strip, friction occurs at the contact portion between the work roll and the material to be rolled (hereinafter referred to as “plate path”), and wear of the portion corresponding to the plate path of the work roll proceeds. Particularly in the case of hot rolling, when the material to be rolled is a steel material, since it is as high as about 800 to 1100 ° C., thermal expansion occurs in a portion corresponding to the plate path of the work roll called a thermal crown. Due to such local wear and thermal expansion, there is a problem that the width direction plate thickness distribution and shape of the material to be rolled are deteriorated, resulting in a decrease in product quality and sheet feeding stability.

  For this reason, a work roll shift method has been put into practical use in which the upper and lower work rolls are shifted by several millimeters in the axial direction for each rolling of the material to be rolled. Note that there are work roll cloths and benders as mechanisms for compensating for roll deflection due to rolling load, but these cannot control a non-uniform profile in the width direction such as wear and thermal expansion.

In the conventional work roll shift rolling method, each time the material to be rolled is rolled, the axial position of the work roll is shifted by a few millimeters at a constant pitch (hereinafter referred to as a shift pitch). A cyclic shift method that turns and continues shifting is widely used.
Since this method is a fixed shift pattern determined by equipment constraints such as shift pitch and upper limit of shift amount, depending on the difference in sheet width between one rolled material and the next rolled material, roll wear or Due to the influence of thermal expansion, there may be an abnormal thickness profile such that the thickness of the edge of the plate becomes excessive (edge high spot) or excessively thin (edge drop).

  On the other hand, as a plate crown control method utilizing work roll shift, as shown in FIG. 3, a pair of upper and lower rolls having a curve whose roll profile is expressed by a function of third order or higher are moved in the opposite directions in the axial direction. Japanese Patent Application Laid-Open No. H10-228688 discloses a method for causing the above to occur. When the upper and lower rolls are respectively shifted in the opposite axial direction, the shape of the roll gap at the material to be rolled changes, and the plate crown and shape can be controlled by the shift position.

Patent Document 2 discloses an optimum shift that provides an allowable range at the shift position of the next material determined on the premise of the cyclic shift method, and minimizes an evaluation function composed of a target value of roll profile and a predicted calculation value within the allowable range. A shift amount determination method for determining the position has been proposed.
In Patent Document 3, an evaluation function determined from a target value and a predicted calculation value of a work roll profile is calculated assuming a shift position of each material to be rolled, and the shift position at which the evaluation function is minimized is rolled in a rolling cycle. A method for determining all planned rolled materials has been proposed.

Patent Document 1 JP 57-091807 A Patent Document 2 JP 06-154823 A Patent Document 3 JP 63-260615 A

However, in the method described in Patent Document 1, since the shift position is determined by the sheet width and rolling load of each material to be rolled, a cyclic shift method that disperses roll wear and thermal expansion in the axial direction is used. I can't.
Moreover, in the method described in patent document 2 and patent document 3, it is characterized by making a work roll profile into a target profile over the whole roll trunk length, and the board path range on the work roll of a to-be-rolled material is characterized. The shift position is not determined in consideration. In other words, when determining the shift position, it does not take into account “where in the work roll profile to roll the material to be rolled”, so depending on the plate width and shift position of the material to be rolled, the edge high spot or edge There is a problem that an abnormal thickness profile such as drop occurs.

  The present invention has been made to solve the above problems, and when rolling the material to be rolled, the thickness in the width direction of the plate is not uniform, especially the width end is too thin or too thick. It is an object of the present invention to provide a method for rolling a metal strip that can solve the above problem, and to realize a schedule-free process in the production of the metal strip stably and reliably.

That is, the present invention is as follows.
[1] In a metal strip rolling line, all the rolled materials scheduled to be rolled in the rolling cycle have a curve whose roll profile is expressed by a function of third order or higher, and complement each other vertically in the axial position. In a rolling method in which rolling is performed by shifting the work rolls in axial directions opposite to each other by a rolling mill provided with a pair of upper and lower work rolls formed by an initial roll curve having a shape, all the rolls scheduled to be rolled in a rolling cycle For materials, assuming an upper limit for the work roll shift pitch and assuming possible work roll shift position combinations, for each of these combinations, the roll gap at the contact portion of the material to be rolled and the work roll is predicted for each combination. The difference between the calculated value and the target value is expressed by equation (1) for one or more evaluation points in the width direction of the material to be rolled.
Is obtained as an evaluation function J1, and the value of J1 obtained for all of the one or more evaluation points is obtained as an evaluation function J2 based on the equation (2), and then J2 is all rolled material of the rolling cycle. After obtaining the total value as the evaluation function J3, the work roll shift position of the combination when it becomes the smallest among the values of J3 for each combination is the work roll shift for all the rolled materials scheduled to be rolled in the rolling cycle. A method of rolling a metal strip, wherein the rolling is determined as a position.
[2] The metal strip rolling method according to [1], wherein a rolling mill provided with the pair of upper and lower work rolls is provided on at least one stand of a tandem rolling mill.

  All the rolled materials to be rolled in the rolling cycle can be shifted in the opposite axial directions, and the roll profile has a curve expressed by a function of third order or higher, and complements each other in the axial direction up and down. By optimally determining the axial shift position of the work rolls of all the materials to be rolled when rolling with a rolling mill provided with a pair of upper and lower work rolls formed with initial roll curves of mating shapes The thickness distribution of the metal strip can be made uniform. As a result, it is possible to employ a rolling cycle in which the width of the sheet, which is likely to cause an abnormality in the crown profile, is assembled from a narrow width to a wide width, and it is possible to perform schedule-free process management with no sheet width restriction.

The evaluation point of the evaluation function defined in the width direction of the material to be rolled of the present invention is shown. The calculation step of the evaluation function of this invention is shown. The work roll of the rolling mill used in this invention is shown. About the Example, the rolling cycle of the board width and board thickness of all the rolling materials is shown. A work roll shift position is shown about an example. The thickness profile of a to-be-rolled material is shown about an Example. About the other Example, the rolling cycle of the board width and board thickness of all the rolling materials is shown. The WR shift position is shown for another embodiment. The thickness profile of a to-be-rolled material is shown about another Example. The surface profile (r ₁ ) and the roll axis direction coordinate (x ₁ ) of the work roll are shown.

Embodiments of the present invention will be described below.
In the present invention, an initial roll curve having a shape that can be shifted in mutually opposite axial directions, has a roll profile expressed by a function of a third order or more, and complements each other in the axial direction. A rolling mill provided with a pair of upper and lower work rolls formed in (1) is used. FIG. 3 shows only a pair of upper and lower work rolls of this rolling mill.
As can be seen from FIG. 3, the work roll has a slightly S-shaped roll profile (roll barrel), and has a shape that complements each other in the axial direction.

Embodiments of the present invention will be described below.
The present invention applies to all the rolled materials so that the roll gap shape at the contact portion (sheet path) between the rolled material and the work roll is the target roll gap shape for all the rolled materials scheduled to be rolled in the rolling cycle. The work roll shift position is determined.

  In the present invention, assuming all possible work roll shift combinations for all the rolled materials scheduled to be rolled in the rolling cycle, the contact portion between the rolled material and the work roll for each of these combinations. The value of the first evaluation function determined by the roll gap prediction calculation value and the target value is calculated for all evaluation points of one or more points in the width direction of the material to be rolled, and these values are all evaluated points. As a result, the value of the second evaluation function is obtained for one material to be rolled. Next, a value obtained by adding the values of the second evaluation function for all the rolled materials in the rolling cycle is obtained as a third evaluation function. Then, the work roll shift position of J3 that takes the minimum value by comparing the values of J3 obtained for all possible combinations of work roll shift positions is the work roll for all the rolled materials scheduled to be rolled in the rolling cycle. Roll is determined as the shift position.

In this invention, as shown in FIG. 1, a 1st evaluation function is calculated | required about one or more evaluation points of a to-be-rolled sheet width direction, and based on this 1st evaluation function, 2nd, 3rd evaluation is carried out. Since the function is obtained, the roll gap in the sheet path range on the work roll of the material to be rolled can be evaluated, and an abnormal sheet thickness profile or the like can be effectively prevented.
Further, in FIG. 1, a flat work roll is shown to clearly show one or more evaluation points A, B,..., F in the width direction of the material plate. Thus, a roll having a curve whose roll profile is represented by a function of third order or higher as shown in FIG. 3 is used.

Hereinafter, a specific example of the evaluation function calculation method in the above invention will be described below.
In the present invention, first, a possible combination of work roll shift positions is assumed for all the rolled materials to be rolled in the rolling cycle. For example, when the number of all rolled materials to be rolled is N, the work roll shift position of the _first rolled material is X ₁ , the second is X ₂ ,..., The Nth is X _N Then, the combination of the work roll shift positions is (X ₁ , X ₂ ,..., X _N ).
Then, X _{1, X 2,} · · ·, since each value of X _N may vary in the extent possible, the combination (i.e. the work roll shift position possible for all the material to be rolled in the rolling schedule in the rolling cycle accordingly Combination).

The evaluation function calculation method of the present invention includes the following steps 1 to 4.
(Step 1)
One or more evaluation points A, B, C... Are defined in the width direction of the material to be rolled, and for each evaluation point, based on the following formula (1) from the predicted value and the target value of the roll gap of the work roll. Thus, the first evaluation function J1 is calculated for one material to be rolled.

The evaluation points are, for example, A (25 mm from the end of the outermost plate), B (50 mm), C (75 mm), D (100 mm), E (150 mm), F (200 mm) in FIG. Suppose that it is at least one point in the plate width direction.
The specific numerical values for the distance from the outermost plate edge of the evaluation point are only examples, and the present invention is not limited to the examples here.

(Step 2)
Based on the following formula (2) for all the evaluation points A, B, C..., The evaluation function J1 of the formula (1) is summed to obtain the second evaluation function J2.

(Step 3)
For all the rolled materials in the rolling cycle, the third evaluation function J3 is obtained by summing up the evaluation functions of the expression (2) based on the following expression (3).

In addition, about the weighting coefficient _ck of Formula (1)-(3), it can determine according to the change of the plate | board width from a previous to-be-rolled material like Table 1 to a next to-be-rolled material, for example. .

(Step 4)
J3 values obtained for all possible combinations of work roll shift positions for all materials to be rolled in the rolling cycle are compared with each other, and the work roll shift position in the smallest case is compared with the rolling value. It is determined as the work roll shift position of all the rolled materials in the rolling cycle of the cycle.
Based on the work roll shift position determined in this manner, all the rolled material in the rolling cycle of the rolling cycle is rolled.

In the above steps, a possible combination of work roll shift positions is assumed for all the rolled materials scheduled to be rolled in the rolling cycle, but for the work roll shift positions, for example, using a random number table, the rolled material It can be determined by assuming a work roll shift position for each.
If you want to set an upper limit for the work roll shift position change amount (work roll shift pitch) for the preceding material to be rolled and the next material to be rolled after this, the combination of work roll shift positions in consideration of the upper limit value Can be assumed.

Even when an upper limit is set for the work roll shift pitch, the number of combinations of work roll shift positions for all the rolled materials scheduled to be rolled in the rolling cycle is enormous, and the evaluation function J1 is set for all of these combinations. Calculate for each evaluation point, then add up all evaluation points to find J2, and then add up all the material to be rolled and from J3, the work roll shift that minimizes the evaluation function J3 Of course, the position may be selected, but in order to reduce the calculation load, it is also possible to determine the work roll shift position that minimizes the evaluation function J3 by nonlinear programming or the like.
The above steps 1 to 5 are shown in FIG.

The evaluation function J1 of step 2 is obtained from the roll gap target value and the predicted value.
As shown in FIG. 1, the target value of the roll gap is a workpiece at a work roll location in contact with each evaluation point on the driven side (drive side) and driven side (work side) on the material to be rolled, for example, points A to F. The difference between the average roll radius and the work roll radius at the center of the length of the work roll is calculated based on the following formula (4), and the total is obtained for the upper and lower work rolls. It is preferable to set the center of the body length of the work roll profile and the left and right evaluation points A to F to be connected by a quadratic curve such as a parabola or an ellipse.

The predicted roll gap can be obtained as follows.
The thermal expansion of the work roll and the wear of the work roll can be predicted and calculated based on, for example, Expression (5) and Expression (6), respectively.

  And about the roll gap shape which excluded thermal expansion and abrasion, the roll diameter is given to the roll whose roll profile is represented by a cubic function as shown in the formula (7), and the roll position of the formula (8) depends on the shift position. The prediction can be calculated as follows.

  Based on the predicted calculation value calculated by the equation (4) for the work roll gap, which is the total of the above three factors for the thermal expansion of the work roll, the wear of the work roll, and the roll gap shape excluding the thermal expansion and wear. In addition, J1 in equation (1) is obtained by calculation.

Examples of the present invention are shown below.
Example 1
F1-F7 is a rolling mill provided with a pair of upper and lower work rolls formed by an initial roll curve having a roll profile having a curve expressed by a function of cubic or higher and complementing each other in the axial direction. The present invention was verified in a hot rolling line having a tandem finish rolling mill provided for all seven stands. Table 2 shows the equipment specifications of the rolling mill.

The present invention example and the conventional example were compared and evaluated with respect to the rolling cycle having the thickness-width configuration shown in FIG.
The evaluation points were three points of 25 mm, 75 mm, and 150 mm from the plate end of the material to be rolled, and the upper limit of the work roll shift pitch was 20 mm.
The bender load was set to 75 tons at the start of rolling, and was controlled according to the load fluctuation during rolling.
The evaluation of the thickness profile of the rolled material after rolling was performed on the 62nd sheet in which the plate width was expanded by about 150 mm from that of the previous rolled material. For comparison with the prior art, the WR shift position was determined by the conventional cyclic shift method and rolled in a cycle having the same thickness configuration and width configuration as in FIG.

  FIG. 5 shows the WR shift position determined by the method of the present invention and the WR shift position by the conventional cyclic shift. FIG. 6 shows the thickness profile of the 62nd plate. In the conventional example, the reverse crown profile is about 20 μm, whereas in the present invention, the reverse crown profile is not generated and the crown profile is good. Was confirmed. In addition, no abnormal profiles or shape defects occurred in the crown profiles other than the 62nd.

(Example 2)
Three stands of F1 to F3 stands in the front stage are provided with work rolls that do not shift in the normal axial direction, and F4 to F7 stands in the rear stage have a curve whose roll profile is expressed by a function of third order or more, The present invention was verified in a hot rolling line having a 7-stand tandem finish rolling mill having a pair of upper and lower work rolls formed of initial roll curves that complement each other in the vertical direction at the directional position.
Table 3 shows the equipment specifications of the rolling mill.

The invention example and the conventional example were compared and evaluated with respect to a rolling cycle having a plate thickness-plate width configuration shown in FIG. The evaluation points were four points of 50 mm, 100 mm, 150 mm, and 200 mm from the end of the rolled material, and the upper limit of the work roll shift pitch was 20 mm.
The bender load was set to 75 tons at the start of rolling, and was controlled according to the load fluctuation during rolling.

  The evaluation of the thickness profile of the rolled material after rolling was performed on the 90th sheet in which the plate width was expanded by about 220 mm from that of the previous rolled material. For comparison with the prior art, the WR shift position was determined by the conventional cyclic shift method and rolled in a cycle having the same thickness configuration and width configuration as in FIG.

  FIG. 9 shows the 90th plate thickness profile. In the conventional example, the reverse crown profile is about 10 μm, whereas in the present invention, the reverse crown does not occur and the crown profile is good. It could be confirmed. In addition, no abnormal profiles or shape defects occurred in the crown profiles other than the 90th.

  In the above description, the example in which the present invention is applied to a tandem rolling mill for a hot rolling line has been described. However, the present invention can also be applied to a rolling line for other metal strips such as a cold rolling line.

Claims (2)

In the rolling line of the metal strip, all the rolled materials to be rolled in the rolling cycle have a curve whose roll profile is expressed by a function of the third order or higher, and the initial shape that complements each other vertically in the axial position. In a rolling method in which the work roll is rolled by shifting in the opposite axial directions with a rolling mill provided with a pair of upper and lower work rolls formed by a roll curve, for all the rolled materials to be rolled in the rolling cycle,
An upper limit is set for the work roll shift pitch, and assuming all possible combinations of work roll shift positions, for each of these combinations, a predicted calculation value of the roll gap at the contact portion between the material to be rolled and the work roll is provided for each combination. The difference from the target value is expressed by the following formula (1) for one or more evaluation points in the width direction of the material to be rolled.


Based on the above, the evaluation function J1 is obtained as the evaluation function J1, and the values of J1 obtained for all the evaluation points of one or more points are expressed by the following formula (2)


Is obtained as an evaluation function J2, and then a value obtained by summing J2 for all the rolled materials in the rolling cycle is obtained as an evaluation function J3. A method of rolling a metal strip, wherein a roll shift position is determined as a work roll shift position for all the rolled materials scheduled to be rolled in a rolling cycle. The metal strip rolling method according to claim 1, wherein the rolling mill provided with the pair of upper and lower work rolls is provided on at least one stand of a tandem rolling mill.